Pneumatic tire



, I 1,632,201, June s. A. STEERE PNEUMATIC TIRE Filed 0ct.15, 1925 "2 Sheets-Sheet 1 i fiw 9 H INVENTOR Samuel A. Steam,

ATTORNEY Patented June 14, 1927.

UNITEDOST'ATES PATENT OF SAMUEL A. STEERE, OF AKRON, OHIO, ASSIGNOR TO THE GOODYEAR COMPANY, OF AKRON, OHIO, A CORPORATION OF OHIO 1,632,201 FICE.

TIRE & RUBBER PNEUMATIC .IIRE.

- Application filed October 15, 1925. Serial No. 62,580.

My invention relates to the art of manu-' facturing pneumatic tires and it has particular relation to tires whose fabric reinforcement includes a cord structure.

()ne object of my invention is to provide a fabricated product which will give improved ser'vice compared with present standards. Y

Another objectofi the invention is to PI0- vide a. satisfactorycord fabric whichmay be spun from a shorter staple cotton.

Briefly, he invention provides for a fabric structure, the individual cords of which are particularly adapted to Withstand the strain and distortion to which a tire is subjected.

' A cord embodying the principles of my invention is characterized by its greater elasticity and durability, higher twist, and a somewhat lower tensile strength than cords of substantially the same unit weight which have been utilized heretofore. I

In order to have a clear understanding of my invention, reference may be made to the accompanyingdrawings, in which;

Fig. 1 is a. perspective cross-sectional view of a tire illustrating a cord fabric carcass such as is involved in the'present invention;

Fig. 2 is an elevational view of a'portion of a cord illustrating the manner in which the subordinate elements are fabricatedto form the yarns, strands, and finally the finished cord or cable; Fig. 3 is graphicalrepresentation illustrating the effect of theidegree of twist on the tensile strength and elongation of a balanced cord; and

Fig. 4 is a graphical comparison of. thestress-strain characteristics, of a cord twist-- ed to avail it of its maximum tensile strength with one embodying the principles of the I present invention.

In its essentials, a cord tire comprises a tread 1 1, and bead portions 12 interconnected by a plurality of plies'13 of rubber impreg nated fabric. In order to reduce the shocks occurring during the life of a tire, a breaker strip'le is often applied between the tread and ,fabric reinforcement. It is the combination resulting from the incorporation of new cord fabric in a rubber tire that is made the subject of this invention. \Vith a few exceptions, it is universal practice in the tire industry to utilize a fabric. the individual cords of'which are made 'up of three progressively twisted elequalified will readily suggest themselves.

Yarn. Strand. Cable.

1 Reverse-.. Rev r e R J 2 Regular Re ular Rgggi-gg, 3 Rever Remflm' Reverse. 4 Regular Reverse Regular.

While the three unit construction is the most popular, two as well as four unit products have been employed. It is .not to be assumed from the illustration in Fig. 2 that the invention applies only to cords wherein five yarnsv are employed to form a strand and three of these strands united to form a finished cable. Nor. is this improvement limited to yarns of any" particular size, for while at the present time the industry favors a 23s. yarn, the principle is equally applicable to 6s, 13s, 18s, 26s and others. For

purposes of exemplification however, and because it isby far the most universally utilized, 'the'cord of 23s/5/3 construction is hereinafter "discussed. 7

Heretofore, the relationship which existed between the spinning of the cord fabric and the life of a tire was unrecognized. Because of this, together with the peculiar character of the spinning industry, wherein the personal element plays so important a. part in the quality and uniformity of the product, tiref manufacturers have seldom stipulated more than the size of the cord which they desires to utilize. The degree of twist and conditions under which the spinning was to be conducted were left wholly to the judgment and experience of the textile engineers. Under these conditions their unvarying procedure was to select the conditions and degree of twist which balance, and uniformity. The first two properties are considered a direct measure of the utility of the cord when fabricated in the finished tire, and are controlling. The last named property merely reflects the condition of the mill and the workmanship and capability of its operators. A well balanced cord whose tensile strength is at. .a maximum is the coveted goal of all tex- However, a six percent variation in the average-tensile strength may be said to cover the-range of good standard practice. It is (llffiCUllEiO state the acceptable variation in balance inasmuch as there is no recognized test which may be employed to measure this property. It is not difiicult, however, to vary the degreeof twist in order to maintam a satisfactory balance without materially afl'ecting the tensile strength and cer tainly without exceeding its factorof tolerance, g I

p The procedure in designing tires is almost entirely empirical. In selecting a cord, the designer calculates the number of plies according to the load towhich the cord member will be subjected when the tire is inflated.- For a -23s/5/3 constructiomthe allowable stress'which .the cord may undergo varies from two to three pounds. Such a cord is capable "of supporting from sixteen to twenty pounds atits ultimate load;

obviously, this provides a high factor of.

safety.

' The lower stressstrain curve of a cord which has been constructed to avail it of its maximum ten .sile strength. It is to be noted that this -I have found characteristic is general and is not-limited to a specific construction. When the stress unit is expressedin pounds, the curve will apply to a 235/5/3 construction. Thus,.at the average breaking load of' 17.5 pounds the cord elongatessubstantially 17.5 per cent of its original length.

7 that by increasing the degree of twist a cord, certain'properties- I are accentuated, which render the cord par- Thus, for example, the elongation may be increased 254:0 35 per cent, and at the same;

ticularly adaptable" for tire construction.

time' the cord is given a harder texture. Ob viously, a change of construct-ion produc ng the increased elongation results in a.- de--;

line-in Fig. 4 is a characteristic crease of the tensile strength of thev oord.' This is illustrated-graphically. in Fig. 3 wherein the elongation, represented by (a) and tensile strength, represented by (b), are plotted against the degree of twist/ It must be stated that the chart applies only to balanced cords and that it is not readily suited to an unbalanced structure. From this it is apparent that the elongation increases rapidly as compared to the decrease in the tensile strength.

To illustrate what is meant by a highly twisted cord, as compared to one having a twist commensurate with a maximum tensile strength, the" following table indicates the changes in specifications which are necessary in order to practice the invention in its preferred form.

Turns per inch in-- Construction.

Yarn. Strand. able.

A 17 1a. 5 1.5 B 21. 25 20. 5 9.65 21. 25 23. 0 a 90 The specifications given under A are designed to produce a cord having a maximum tensile strength, which would correspond to an elongation at the breaking load of substantially 17.5 per cent. Those given .four 'yarns, the number of turns per inch in the strand and cable "twists are substantially higher than those of a 23s/5/3 construction.

It is diflicult to state a twist specification as being a fixed standard because of the many variables which enter into ,the con;

=struction, of' a satisfactory cord product.

For this reason it is belived thatno standard specifications have ever been recognized,

but a cord having a maximum tesil'e strength has a definite twist characteristicand' it may be employed or purposes of comparison. Hence by taking the difference in the turns per inch which have been utilized in constructing ,thel'yarns of a cord having a" maximum tensile strength and the yarns 'ofa cord constructed in accordance to the principles herein set forth,.,and expressing the difference as a percent of the turns uti-' lized in standardpractice, one has a measure of the change necessaryffior that twist to practice the invention in its preferred form.

As indicated by examples A and B the difference in the yarn twists of the old and new constructions is 4.25 turns per inch. This expressed as a per cent of the recognized practice indicates that the change is substantially 25 per cent. In like-manner,

the change in the strand twist will be found to be 24.3 per cent and that of the cable twist 28.7 per cent. I

The twist specifications, such as have been referred. to, may be determined by counting the turns per inch necessary to unwind a given length of cord completely.

The strands which result are subsequently likewise untwisted and the number of turns determined in the same manner. The same is true of the individual yarns or singles. It is appreciated that this method of analy-fi sis is not exact in that it does not take into consideration the contraction and extension of the subordinate twists relative to' the length of the original cord sample, yet-the method is recognized and employed in the textile strength art. The tensile of the cord product was determined by applying a load be caused to 'recede at a rate of fourteen inches per minute. Of the test sample, a

fifty centimeter length is laid offv and the elongation thereof is recorded at the breaking load. It is to be noted that in conducting all of the physical tests the cords are.

first allowed to come to equilibrium'at F. in an atmosphere having a relative humidity ranging between 63 and 65 per cent. conditions the cord will have a six per cent moisture content. f

Referring again to my .cord, it may be characterized in that the cable twist has 28 per cent more turns per inch than a cord having a like number of subordinate units, but which has been twisted to avail it of its maximum tensile. Or by adding the percentage increase in the number of turns per inch of the strand and cable twists, which in this instance is 53 per cent, one has an additional distinguishing feature of the present invention.

for thethree twists be divided by three the It will be found that under these In t e same manner the -.total additive percentage increase of 78 per 5 cent maybe utilized to characterize my product. The twist specifications hold only for result expresses an integrated value of the increase in degree of twist for the three operations. It cannot be said that the percentage increase expresses the increased number of turns in any twisting operation, but inasmuchas the limits within which the textile-engineers must operate in order to secure a balanced cord are not wide, this integrated value is of considerable significance, particularly inasmuch as it is not limited to any cord construction or yarn size. It will be noted that Fig. 3 refers'to ,the degree'of twist, in terms of integrated twist magnitude. If the cord having a maximum tensile strength is arbitrarily given the value of 100, acord which has been constructed according to the principles of my invention will have an elongation and tensile strength corresponding to one whose integrated twist-is equal 'to'lOO plus 7 8 per cent or substantially 126 per cent.

to balanced cords generally and serves to illustrate by comparison the marked difference instress-strain properties which dis tinguish cords constructed according to my.

The graph illustrated in Fig. 4 applies invention from'those constructedsaccordingi to practices heretofore employed. Further more, the curves are applicable to any cords.

--when interpreted relatively. Thus, instead of stating the stress units in pounds, in

=which case they are applicable to a 2 3s/5/3 construction, ,they may be interpreted relatively. In so doing the lower curve Wlll always represent the stress-strain character istic of a balanced cord twisted for the purpose of securing the ultimate I strength, whereas the upper curve is descriptive of a cord of substantially thesame unit weight embodying the principles-of my invention.

An additional property which characterizes this invention is that. of its durability as measured bya machine, such asv described in patent application, Serial No. 628,611. I have compared results of tests on cords constructed to avail them of their maxilit)" mum tensile strength with those of my more highly twisted construction. The average results for a' cord of 23s/5/3 construction are tabulated below. In' these tests, the cord was caused to oscillate about a half inch pulley at a rate of 340 cycles per minute while under a tension of 4.7 5 pounds.

From these figures it will be apparent that the higher twist increases; the durability even though the productitself has a somewhat lower tensile strength,

It has been found that the life of the the condition of the cord prior to the test.

- practice. ture along with its harder and more resistive For this reason, the samples which were tested were under no stress before themagnitude of the particular property was determined. The durability testmeasures an additional property, which distinguishes the present invention.

VVhema cord, such as has been described, is incorporated in a tire, the new properties which-have been imparted to-it bring about reactions entirely foreign to those of cords constructed according to. present day For example, its more elastic nacharacter permits it to withstand more 'eflI'ectively the strains to which-a tire is subjected.

Summarizing,

I fabric resists compression, favors elongation, is not easily subjected to chafing action,

. tively when subjected to fiexure' and conpractice;

traction, than fabric which has been constructed according to I the recognized I have prepared and tested tires whose fabriecarcasses embodied the principles of my invention-and have compared the results with tires constructed similarly with the-exception of the degree of twist in the cords. The results indicate that an increased mileage of from to over 100 per cent may be enjoyed by utilizing the more highly twisted structure. These'tests were made under actual road conditions.

adm N I t- R0 usage Inc ieased 0. 0 ODS 111C- 1 m1 cage Test bile plies. 121011. O New in twist. twist.

A 30 344 4 23'3 5/3- 5,279 13.... 303% 4 2334413--.. 13,954 120- 0 31:4 6 233/5/3. 4,724 13.1. 3134 6 23's/4/3--. 8,383 77 E 321% '0 233 5 3,750 8,340 135 32x4% 6 23s/5/3 3,110 10,230 220 (1.... 323494 6 2331/5 3-.-. 3,240 12,730 203 H--- 32x4% 0 23's/5 3. 010 6,235 107 1 33x5 8 23's/5l3. 6,734 I-.. 33x5 3 23s/4I3 10,827 61 K-.. "40x8 12 23s/5/3- 6,836

40x8 12 23'5 5/3 16,925 147 4038 12 233 5 8,840 20,480 132 N 40x8 12 23s/5/3 7,290 13,350 152 o 40x8 12 23s/5/3..-.. 5,040 10,620 79 I been drawrr between tires embodying the it is to be observed that my" and, as a whole, reacts less destruc- In several instance the comparisons have" yantage. Nevertheless themileage results are decidedly in favor ofthe smaller cord. In other instances, the tests were conducted in such manner as to favor the present day or old construction. For. example, the tire mileage listed for the old construction in test 0 is the average obtained from eleven tires. In conducting. the experiments many"- more tires, embodyingthe same construction were employed but where the test ended be causeof bruises, snagging'and similar failures which have no bearing, upon the life of the fabric, the'mileages were not included.

iOnly' those tires which failed as a result of fabric fatigue were utilized in making up the average? On the other hand, of the three tires which were constructed in the same manner as the eleven whose average mileage was 5,940 miles but whose cord construction embodied-the principles of my invention, one failed as a result of a bruise,

another a; snag and the other as a result mileage results of M,- N, and O. The I first two were conductedunder similar-conditions and the results indicate that the fabric gave 132 and 152 percent respectively longer life. tire embodying subjected to a load the tire cmbodyi'n subjected to an a dred pounds. appear to be a discrepancy since the life has been prolonged merely an additional 79 per cent of that of the old "construction as compared to the other tests, which easily doubled the life of the former construction. Other interesting features ofthe test might be narrated, but they are unnecessary to the the 'old construction was of 4,500 pounds whereas the new construction was ditional load of five hunpractieing of the principles which have been hereinaboveset forth.

As stated above, these result's'are the averages; which have been. obtained under road conditions. For-"this reason other destructive agencies were present which undoubtedly had a marked effect in determining' the life of the tire. It may safely be stated, however-,that inasmuch as the tests were run under like conditions, the results 'f01 this marked improvement. To further substantiate this contention, the type of failures was cons1stent. In the case of the old construction, the shoulder ,break de 'termined the life of the tire, whereas tires embodying cords constructed according to In the latter case, however, the- This accounts for what might prove .that the fabric alone is responsible the principles of my invention were giving service even after the tread had beenworn to the breaker strip without any indication of shoulder break weakness.

While actual road tests are, in the fina analysis, the best measure of the quality of a tire, it must be admitted that many factors are present which may defeat the purpose of a test, as in this case to determine the value of a fabric. In order to obviate these disturbing'influences, and to ascertain the value of the new construction by other means, a large number of runs have been made on an artificial road tester. The results are tabulated below.

N I I C t Road-mileage. meilieased 0.0 0118 rucm 0388 Test size: plies. tion. New in twist. twist.

P 32x04 6 2sZs 5 a 5,775 12,990 126 32mg 6 ass/513.- 1,430 13.530 82 3... mm a ass/513.- 5 500 9,100 16 S... 3224% 6 23S/5/3..-.. 2,890 5, 910 104 'r 32x4 6 23sl5/3 3, 560 7,320 120 11.... 321434 a eras 3.-.. 2,430 4, 690 93 It must be stated that. the .mileages are not comparable with those obtained under actual road conditions inasmuch as the cleated surface over which the the must pass is far more severein its action on the fabric reinforcement than an average road.

Numerous comparative tests indicate that onemile on the testing machine is equivalent to two orthree miles under actual service conditions. a

In practicing the principles of my invention, it isvpossible to use a less expensive grade -.of cotton. The long staple fibers which were believed to be essential to the life of a tire fabric are now no longer necessary. The results of experiments indicate that the controlling factor which determines the life of a tire embodying the principles of this invention is no longer its fabric structure, butdepends largely on the wearing ability of the tread. I believe that the new and desirable properties imparted to a cord,

which is incorporated in a tire resides in its increased durability and its ability to undergo greater elongation. Nevertheless, I do not limit myself thereby. Moreover, any theories which I have set forth in attempting to explain the reactions and mechanics of cords incorporated in a pneu-- matic tire arenot to be held as limitations of my invention.

Althoughl have described-the principles tended to cords having'other yarn numbers and combinations whether twisted wet or dry and that they may be subjected to wide variations without departing from the scope thereof. I desire, therefore, that limitations be imposed only to accord with prior art'and the appended claims.

What I claim is:

1.. In a tire, a cord fabric carcass embodying cords having a substantially ,higher twist than that-Which is necessary to produce the maximum tensile strength therein.

2. In a pneumatic tire, a cord fabric carcass embodying cords Whosecable has substantially eighteen percent more twist than that necessary to produce a cord of maximum tensile strength.

3. In a pneumatic tire, a cordfabric carcass embod ing cords whose cable has substantia'lly eighteen per cent more twist than that necessary to produce a cord of maximum tensile strength, and an elongation at breaking load of more than twenty per cent.

4. In a pneumatic tire, a cord fabric carcass embodying cords whose strand has substantially eighteen percent more twist than that necessary to. produce acord having maximum tensile strength, and an elongation at breaking load of more than eighteen per cent.

5. A tire fabric embodying cords having relatively high degree of twist with respect to the twist required to produce cords of maximum tensile strength.

6. A tire fabric embodying cords having a substantially higher degree of twist than cords of the same unit weight which have been twisted to avail them of their maximum tensile strength.-

7. In a pneumatic tire, a cord fabric carcass embodying cords each so twisted .as to produce a substantially greater elongation at breaking load than a similar cord of the same unit weight-so twisted as to avail it of its maximum tensile strength.

8. In. a pneumatic the, a cord fabric carcass embodying cords of 23s/5/3 construction thecomponent parts of each of which are so twisted as to produce an elongation at breaking load of at least 21 percent.

9. In a neumatic tire, a cord fabric caran elongation at breaking load of at least 21 percent.

In witness whereof, I have hereunto signed my name.

SAMUEL A. TS'REE E. 

